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Pyxidinopsis minuta
From Fensome et al., 2019:
Pyxidinopsis minuta Duxbury, 2018, p.190–191, pl.5, figs.9,13,17–18; pl.6, figs.14–15. Holotype: Duxbury, 2018, pl.6, figs.14–15. Age: early Valanginian.
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Original description Duxbury, 2018:
Plate 5, figures 9, 13, 17, 18, Plate 6, figures 14, 15
Holotype: Plate 6, Figures 14, 15.
Paratype: Plate 5, Figures 9, 13.
Type Locality: Division D4D, lower Valanginian, Speeton Clay, Speeton, England. Holotype: Speeton Division D4D. E.F. P43.1. Paratype: Speeton Division D4D. E.F. N47.2.
Derivation of Name: From the Latin minutus, little, small – in reference to the very small size of this species.
Diagnosis: A very small, delicate, spheroidal to ovoidal dinocyst, which is smooth and covered in a reticulum of varying mesh size; the reticulum is often incomplete. Slightly raised peaks mark each junction point within the reticulum. The reticulum often shows some alignment reflecting the cingulum. The archeopyle is single-plate precingular.
Dimensions: Holotype: Length – 38 μm. Width – 38 μm.
Paratype: Length – 35 μm. Width – 35 μm.
Overall: Length – 43 (39) 33 μm. Width – 41 (37) 33 μm.
Specimens Measured: 17.
Remarks: Pyxidinopsis minuta n. sp. is significantly smaller than Pyxidinopsis challengerensis Habib 1976 and has a surface reticulum usually of a larger mesh size, although this is variable. The possession of raised junction points within the reticulum of P. minuta n. sp. appears to be a characteristic absent from P. challengerensis. Although there is some alignment of surface features suggestive of a cingulum, P. minuta n. sp. tends to be randomly oriented, and the delicate cyst is easily-folded, so that no interpretation of the plate arrangement has been possible.
The very limited range of Pyxidinopsis minuta n. sp. at Speeton is between Beds D6C and D4C, straddling the Berriasian/ Valanginian boundary (text-fig. 2), and it was common in Unit D4D, at the base of the Valanginian. This appears to be a similar range to the “Berriasian to Valanginian or Hauterivian” age quoted by Habib (1976) for P. challengerensis.
Pyxidinopsis minuta Duxbury, 2018, p.190–191, pl.5, figs.9,13,17–18; pl.6, figs.14–15. Holotype: Duxbury, 2018, pl.6, figs.14–15. Age: early Valanginian.
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Original description Duxbury, 2018:
Plate 5, figures 9, 13, 17, 18, Plate 6, figures 14, 15
Holotype: Plate 6, Figures 14, 15.
Paratype: Plate 5, Figures 9, 13.
Type Locality: Division D4D, lower Valanginian, Speeton Clay, Speeton, England. Holotype: Speeton Division D4D. E.F. P43.1. Paratype: Speeton Division D4D. E.F. N47.2.
Derivation of Name: From the Latin minutus, little, small – in reference to the very small size of this species.
Diagnosis: A very small, delicate, spheroidal to ovoidal dinocyst, which is smooth and covered in a reticulum of varying mesh size; the reticulum is often incomplete. Slightly raised peaks mark each junction point within the reticulum. The reticulum often shows some alignment reflecting the cingulum. The archeopyle is single-plate precingular.
Dimensions: Holotype: Length – 38 μm. Width – 38 μm.
Paratype: Length – 35 μm. Width – 35 μm.
Overall: Length – 43 (39) 33 μm. Width – 41 (37) 33 μm.
Specimens Measured: 17.
Remarks: Pyxidinopsis minuta n. sp. is significantly smaller than Pyxidinopsis challengerensis Habib 1976 and has a surface reticulum usually of a larger mesh size, although this is variable. The possession of raised junction points within the reticulum of P. minuta n. sp. appears to be a characteristic absent from P. challengerensis. Although there is some alignment of surface features suggestive of a cingulum, P. minuta n. sp. tends to be randomly oriented, and the delicate cyst is easily-folded, so that no interpretation of the plate arrangement has been possible.
The very limited range of Pyxidinopsis minuta n. sp. at Speeton is between Beds D6C and D4C, straddling the Berriasian/ Valanginian boundary (text-fig. 2), and it was common in Unit D4D, at the base of the Valanginian. This appears to be a similar range to the “Berriasian to Valanginian or Hauterivian” age quoted by Habib (1976) for P. challengerensis.